1. Field of the Invention
The invention concerns methods and apparatus for the control of the shifting processes of a vehicle transmission.
2. Description of Related Technology
Drive lines, especially drive lines with automatic transmissions which operate according to the principle of a torque converter with external power branching, in combination with connected mechanical working points, shifting programs with fixed switch points, or simple acceleration-dependent shifting programs are known. In the former, full load shifting normally occurs in the upper rpm range of the engine, n,. The shifting up, which is decisive for the fuel, occurs at about 80 to 90% of the nominal engine rpm. As a result, larger engine power is utilized to produce better acceleration of the vehicle, which may be necessary on a slope or when there are many passengers in the vehicle, especially in the case of buses. However, this also results in a higher fuel consumption because, at a higher rpm, the engine operates in a less favorable region of the characteristic (see e.g., FIG. 3 showing the engine characteristic of consumption as a function of load and rpm). In a braking operation, that is, in gear but with the gas on zero, the engine rpm has no influence on fuel consumption, since the fuel supply is stopped. In order to avoid vibration between gears, down shifting generally occurs at a lower rpm than up shifting, except for during kickdown. Furthermore, the shifting programs with fixed switch points are designed so that, for partial load or without load, certain shift points occur at lower engine rpm than at full load. In addition, a so-called overstep or kickdown function can be provided which opens up the possibility of running the gears to the maximum permissible engine rpm. Such shifting programs with fixed shift points operate either in a power-oriented manner characterized by increased fuel consumption, or they are operated very much oriented to consumption.